Spray-on coating helps keep bananas from spoiling

Scientists have developed a hydrogel that lengthens the shelf life of bananas (Photo: Shutterstock)

Just about everyone loves bananas, but there is one problem with the things – they have a way of becoming overripe before they can be eaten. Yesterday, however, a scientist from China’s Tianjin University of Science and Technology announced the development of a spray-on coating that is capable of keeping picked bananas fresh for almost two weeks.

Like other fruit and vegetables, bananas remain “alive” after being harvested, and respire (or breathe) through their skin. The faster that a fruit respires, the faster that it ripens. Unlike many other fruits, however, the respiration rate of bananas does not slow down after they’re picked. This causes them to ripen more quickly than most fruits, to the point that they often become brown and mushy before they’re consumed.

The coating, which is a type of hydrogel, works by slowing down respiration and killing a type of bacteria that causes the fruit to rot. Its key ingredient is chitosan, which is a compound found in crustacean shells – something that the seafood industry generates plenty of. Researchers have also looked into using chitosan for applications such as biocompatible transistors, self-healing paint, and virus filters.

When a team led by Dr. Xihong Li sprayed the hydrogel onto green bananas, they remained unspoiled for up to 12 days. How long bananas normally last is somewhat subjective, as different people like them at different stages of ripeness, although generally one week is about their maximum shelf life.

Li envisions a commercial version of the coating being used by consumers, supermarkets, or during transport. He presented his findings in Philadelphia, at the 244th National Meeting & Exposition of the American Chemical Society.